This invention is in the field of electrically operated valves or solenoid valves. More specifically, the invention is a solenoid valve incorporating an improved sleeve assembly.
Solenoid valves are well developed in the art. A basic solenoid valve is an electromagnet so arranged that when current is applied to an electrical coil (when the valve is "energized") a plunger either opens or seals an orifice, thereby controlling the flow of fluid. The simplest solenoid valve has four basic functional parts: a solenoid coil, a valve body, a sleeve assembly and a plunger or armature. The coil surrounds the plunger which may have an insert of a soft synthetic material at one end. The valve body has an orifice which is sealed by the insert in the plunger. The orifice is opened or closed by movement of the plunger. The coil causes the plunger to move when the coil is energized. When the coil is de-energized the plunger is returned to its original position by means of a spring. When current flows through a coil of wire it produces a magnetic field around it. The strength of this magnetic flux depends upon the amount of current flowing and the number of turns in the wire.
The prior art sleeve assembly comprises a tube generally manufactured from nonmagnetic stainless steel which is welded into a first end piece, a magnetic stainless steel flange. The first end piece is adapted such that it is screwed into the body and seals the body to the sleeve. The plunger is located on the longitudinal axis of the sleeve and moves along the axis to open and close the valve. The other end of the sleeve has a second end piece welded to the tube. The second end piece, a stop, forms a portion of a path having low magnetic reluctance to form a magnetic path which exists when the solenoid is energized. The prior art three-piece sleeve is of a relatively complex construction and with attendant possibilities of failure. As it is a three-piece sleeve assembly, there is potential weakness at the welded joint where the sleeve is joined to the flange. In common solenoid valve construction, two forces may be imposed upon this first joint. First, the sleeve assembly forms part of a pressure chamber containing fluid which flows through the inlet port. Underwriters Laboratories and Canadian Standards Association requires the sleeve assembly to withstand 5 times the rated pressure of the valve. Secondly, in a number of common valve constructions, the sleeve assembly is often utilized to retain the body and the solenoid coil in place, this construction causes a constant static pressure upon the welded joint. Applicant's invention involves elimination of the welded joint between the tube and the flange. This simplified construction offers the potential for increasing the strength of the solenoid valve and decreasing the cost.